The concept of reinforcing timber for improving the strength and stiffness thereof at a reasonable cost is well known, dating from at least the late 1800's. Since then, numerous varieties of wood and wood-based materials, that have been "engineered", so as to be reinforced for shear and flexure, have been disclosed. Most prevalent among these has been those varities of wood and wood-based materials that have been flexurally-reinforced.
Flexurally-reinforced wood beam assemblies may be either "prestressed" or "unprestressed". The term "prestressed" refers to those wood beam assemblies into which stresses have been induced (by "prestressing") during the assembly thereof. The term "unprestressed" refers to those wood beam assemblies that have been assembled without any stresses having been induced therein.
There are two broad categories of unprestressed, flexurally-reinforced wood beam assemblies. The first of these are the flitch beam types having vertical reinforcement. The second of these are the types having nonvertical (i.e., horizontal) reinforcing elements, such as flats, rounds, bars, tapes and wires.
Prestressed flexurally-reinforced wood beam assemblies may be either "post-tensioned" or "pretensioned" with or without material, such as bars or wires. In a "post-tensioned", prestressed wood beam assembly, stress is transferred to the wood beam assembly through end bearing plates.
In a "pretensioned" prestressed wood beam assembly, material is highly stressed and then bonded while stressed, so that the stress is transferred to the wood beam assembly through the bond.
Particularly common and attractive varieties of flexurally-reinforced wood beam assemblies include I-beams, T-beams and L-beams. Such assemblies are used as flexurally-loaded beams for joists to support, for example building roof structures and the like. Often, such beam assemblies are compound wooden structures including a lower chord, an upper chord and a web therebetween. Examples of such wood beam assemblies, as well as other closely-related beams, are disclosed in the following United States Letters Patent:
______________________________________ Inventor U.S. Pat. No. Year of Issue ______________________________________ Troutner, et al. 3,894,908 1975 Sensen 4,334,346 1982 Bloys 4,463,887 1984 Reppel, et al. 4,500,378 1985 Knowles 4,501,102 1985 Curtis, et al. 4,615,163 1986 Knowles 4,637,194 1987 Lines 4,720,318 1988 Lines 4,846,923 1989 ______________________________________
While wood beam assemblies, and in particular flexurally-reinforced wood beam assemblies, are extremely useful for their purpose, the handling and assembling of such assemblies has proven problematic, especially "on-site" where such handling and assembly necessarily occurs. In particular, the devices of which I am aware that are provided for such handling and assembly are of such a size and complexity that they are neither cost-effective nor is their use feasible in many situations. Further, such devices do not possess sufficient adjustability to permit different varities of wood beam assemblies, having the various shapes, structures and dimensions as required by the job, to be produced thereby. Due to the equipment needed to provide the requisite prestressing pressure, these problems have been especially acute where prestressed assemblies are involved.
Other problems that are encountered with devices of which I am aware for producing wood beam assemblies, and in particular flexurally-reinforced wood beam assemblies, are: (1) those devices of which I am aware only produce assemblies that are constructed by gluing and none are provided for the use of mechanical fasteners in conjunction with or in place of such gluing; and (2) the devices of which I am aware all require the use of additional apparatuses, such as curing ovens and/or clamping racks, to produce the desired wood beam assemblies. In this respect, none of the devices provided produce a complete finished assembly. The provision of a device which can produce assemblies that are constructed using, i.e., mechanical fasteners (such as staples) in addition to or in place of adhesive (such as glue) not only provides the complete assembly with additional strength but also reduces the "down-time" that would otherwise be required in order to let the adhesive properly set and/or dry. The provision of a device that is self-contained, being capable of producing a complete finished assembly, also reduces labor and space requirements.
Accordingly, it can be seen that there remains a need for a device for the "on-site" production of wood beam assemblies, and in particular flexurally-reinforced wood beam assemblies, which device is of a simple construction, size and operation, and which device is readily adjustable for producing various wood beam assemblies having the various sizes, shapes and dimensions needed. It can further be seen that there remains a need for a method for producing such wood beam assemblies using this device.